Method of and means for removing gaseous impurities from electric discharge tubes



June 12, 1934. H. DAWSQN 1,962,138

METHOD OF AND MEANS FOR REMOVING GASEOUS IMPURITIES FROM ELECTRICDISCHARGE TUBES Filed Sept 17, 1951 INVENTOR Zea. 17. Da wson ATTORNEYPatented June 12, 1934 METHOD OF AND MEANS FOR REMOVING GASEOUSIMPURITIES FROM ELECTRIG DISCHARGE TUBES Leo H. Dawson, Washington, D.0.

Application September 17, 1931, Serial No. 563,346

3 Claims. (Cl. 176--2) (Granted under the act of March 3, 1883, asamended April 30, 1928; 370 0. G. 757) This invention relates to amethod of, and means for, removing gaseous impurities from electricdischarge tubes, and has for its object to provide a means and methodwhereby the neces- 5 sity for long aging and treatment of such tubes tofree them from water vapor and various gases will be obviated.

The single figure of the drawing shows the present invention applied toa luminous sign tube,

With certain parts in section.

In the manufacture of vacuum tubes, electric lamps, tubes for electricsigns, etc., which are evacuated and then filled with one o! the inertgases such as neon or argon, it is necessary to remove completely all ofthe active gases such as oxygen, nitrogen, etc., and water vapor fromthe tubes and carefully purify the inert gas with which the tube is tobe filled. In previous manufacturing methods, the tubes were then bakedand aged for a considerable period under the action of an electricdischarge. The method herein disclosed obviates much of the workinvolved as compared with other ,methods and very materially shortensthe time required in the manufacture of such articles.

My invention is based upon the fact that misch metal, which is composedessentially of cerium, lanthanum, neodymium and praseodymium, has theproperty of uniting very readily with bydrogen, nitrogen, oxygen, otheractive gases and water vapor under the influence or an electricdischarge, while the inert gases have no tendency to react with themisch metal.

The drawing shows a tube 1 for an electric sign, though it is to beunderstood that this is by way of illustration only and not oflimitation. Electrodes 2 are sealed in the tube to provide for theelectric discharge in the apparatus when in use. Tube 3 is connected toa vacuum pump during the steps of manufacture concerned with this methodand is provided with a stop cock 4 to shut off the space within the tube1 from the pump.

The auxiliary discharge device now to be described may be connected atany point to the article to be evacuated. It consists of a bulb 5connected to the discharge tube 1 by a tube 6. Electrodes 7 are sealedinto bulb 5, the said electrodes being made of aluminum to preventcathodic disintegration. Sections 8 of misch metal are inserted intoelectrodes '7. These sections are preferably about one inch long,and thetwo sets of such sections are separated by about four inches, thoughthese dimensions are not critical and may be varied within considerablelimits. V

The apparatus is connected as shown, and the tube 1 is filled with thedesired inert gas at suitable pressure. A discharge between theelectrodes 0 7 is set up and the tube 1 is evacuated to the desireddegree, the discharge being continued until the active gases in the tubehave combined with the misch metal to the extent that the atmosphere intube 1 ism the requisite degree of purity. 55 This method is especiallyeffective in freeing the tubes of water vapor, which is usually the mostdifflcult to remove. I

The herein described invention may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

I claim:

1. An apparatus for removing active gases from an electric dischargetube, comprising an. auxiliary tube adapted to be immediately connectedto the space within said discharge tube between which an electricdischarge may be set up, aluminum electrodes in said auxiliary tube, andpieces of go misch metal inserted in said electrodes.

2. An apparatus for removing active gases from an electric dischargetube containing inert gas that is to remain in such tube during usethereof, comprising an auxiliary tube immediately con- 35 nected to thespace within the said discharge tube and disconnectible therefrom bysealing of! the connecting portion, electrodes in said auxiliary tubebetween which an: electric discharge may be set up, said electrodesbeing of metal substantially unaffected by cathodic disintegration andpieces of misch metal inserted in said electrodes.

3. An apparatus for removing active gases from an electric dischargetube containing inert gas that is to remain in such tube during usethereof, comprising an auxiliary tube immediately connected to the spacewithin said discharge tube and disconnectible therefrom by sealing ofthe connecting portion, electrodes in said auxiliary tube between whichan electric discharge may be set up, said electrodes being of metalsubstantially unaffected by cathodic disintegration and pieces of mischmetal projecting from each electrode toward the other electrode.

LEO H. DAWSON. 05

